The present invention relates to a method of detecting the so-called moire effect during spinning of yarns and the like, as well as to a device for carrying out this method.
To an ever increasing extent, spinning with spindles is being replaced by the spindle-less spinning method using a rotor. This new rotor spinning method entails new spinning defects in the spun threads or yarns, and which have been unknown before. Such defects occur periodically, for example, due to the fact that, at a certain location on the inside of the rotor, an adhesion by resin or the like takes place, and thickened and thinned, regularly spaced portions are produced in the thread or yarn, resulting from a material displacement caused by the local pressure in the resined zones. It is clear that the periodic location of such a defect depends on the respective circumference of the rotor. In this connection, one speaks of the so-called "moire effect."
In spinning processes with spindles, periodically occurring defects, or the moire effect, respectively, have not yet been observed. In such processes, it is rather individual thicker and thinner portions which occur at irregular distances, and special devices have been developed for monitoring those defects. As soon as such a thickened or thinned portion exceeds a predetermined size, the defect is indicated by an associated thread monitoring device. Thereupon, suitable measures are taken, for example, the thread is cut, the defective portion is removed and the two ends of the thread are connected again. Thread monitoring devices of the prior art are designed so that only individual defective portions, i.e., variations of the cross section of the thread, which have a certain length and exceed the admitted tolerence, are taken into account.
The so-called "moire effect" means that each thickened or thinned portion extends over only a short length of the thread so that, while using known thread monitoring devices, the indication of the defects is suppressed, irrespective of their thickness.